We propose to strengthen our capacity to develop, implement, and evaluate data- and theory- driven HIV prevention interventions among men who have sex with men (MSM) in China. An estimated 650,000 persons were living with HIV in China in 2005 and transmission is shifting from injection drug users to populations at risk through sexual transmission. MSM in particular may be experiencing a rapid rise in HIV prevalence right now. In Beijing, HIV prevalence rose from less that 1% in 2004 to over 5% in 2006. HIV prevalence among MSM in Chongqing has already been measured over 15%. While grassroots community- and state- supported prevention programs for MSM are proliferating, they generally have not been guided by rigorous epidemiological data or by theory-based prevention approaches. We propose a four year program to progressively improve the theoretical foundation for HIV epidemiological surveys, prevention programs, and intervention research for MSM in China. The context of our effort will be three serial cross-sectional respondent-driven sampling (RDS) surveys, enhanced with specific training in behavioral research, formative research to adapt and validate detailed behavioral instruments for China, and assessment of the coverage and impact of existing prevention programs for MSM in Beijing and Chongqing. In addition to enhancing our capacity to conduct future large scale randomized controlled trials of HIV prevention interventions, the data collected through this proposal will have immediate applications in targeting the factors and behaviors driving HIV transmission among MSM in our country. By virtue of our team's leadership of locally and internationally funded programs for MSM, we are poised to rapidly incorporate findings into on-going efforts. PUBLIC HEALTH RELEVANCE: As one of the first study conducted among men who have sex with men, the project will help understand HIV/AIDS epidemic among this population in China. It will also help identify high risk group, develop suitable survey tool to investigate risk behavior of men who have sex with men, as well as evaluate the effectiveness of ongoing programs in study areas.